Power semiconductor devices are used as switches in power electronic circuits for switching on and off loads supplied with high currents. Usually power semiconductor devices are able to carry a high electric current in a conductive mode and to withstand high blocking voltages in a reverse blocking and/or forward blocking mode. Edge termination structures smooth electric field profiles in an edge area surrounding the active element area in the blocking mode such that the maximum electric field strength in the edge area at least approximates the maximum electrical field strength in the element area. The edge termination structure of a semiconductor device with an n type drift layer may include field electrodes arranged in trenches and p type zones directly below and adjoining the trenches. The p type zones smooth the curvature of equipotential lines in the edge area.
It is desirable to improve the reliability of semiconductor devices.